Graphene

The 2010 Nobel Prize for Physics went to the University of Manchester’s Andre Geim and Konstantin Novoselov for their experiments with graphene, the thinnest material in the world. But what exactly is it, and what could it be used for?

Carbon, but not as we know itGraphene is one of several forms of carbon known as its “allotropes”. Allotropes are structurally different forms of the same element, in which the same atoms bond together in different ways. For example, molecules of oxygen can bind together as two atoms – O2, which makes up a fifth of Earth’s atmosphere – or as three atoms, ozone, which protects us from ultraviolet radiation despite there only being a tiny amount of it.

In the case of carbon, aside from soot and charcoal, whose atomic structure is not regular and has no order, the most commonly known forms are diamond, graphite, and the fullerenes. In diamonds, the atoms are arranged in a tetrahedral lattice. The atoms of graphite are sheets of hexagonal lattice, while fullerenes are similar lattices arranged into shapes such as balls (Buckminsterfullerine) or cylinders (carbon nanotubes). The different forms have different properties: diamond is electrically insulating and hard; graphite is an electrical conductor and is soft – hence its use as pencil “lead”.

One atom thickLike graphite, graphene’s atoms are arranged in a hexagonal lattice. What distinguishes it is that rather than being made of stacked layers, graphene is one single layer just one atom thick.Andre Geim, winner of the Nobel Prize in Physics for his experiments on graphene.

There are several ways graphene can be produced. The method used by Andre Geim was to peel layers away from graphite using sticky tape until he had a single layer. This exfoliation was done mechanically and the flakes of carbon were deposited on a piece of silicon. Single-atom layers were then found using a microscope.

It’s also possible to “grow” graphene on other substances such as silicon carbide, or on metals. Some of the most important properties of the material have been found in graphene produced this way.

What could graphene be used for?Graphene is one of the strongest materials known, conducts heat better than diamond, and may conduct electricity better than silver. As it’s two-dimensional, it could be used to detect single molecules of a gas – if a gas molecule were to adhere to a sheet of graphene there would be a local change in the electrical resistance. This could also be useful for detecting microbes.

Many of the proposed applications are in electronics and computing. Its electronic properties have led some to suggest using graphene to make transistors for high-speed electrical circuits, and ultimately to replace silicon in microchips.

At the same time, research in China discovered that graphene has some antibacterial properties and is effective at killing E Coli bacteria, leading to suggestions for its use in hygiene products.

All of this is remarkable for a material produced by, in the words of Geim’s fellow materials scientist and the Royal Institution’s 2010 Christmas lecturer, Mark Miodownik of King’s College London, “mucking about in a lab”, and is a testament to the value of blue-skies research.